1. Field of the Invention
The present invention relates to a device for generating an infrared image, comprising a screen transparent in the infrared and supporting a plurality of pixels made from a material having high emissive power in the infrared and means for selectively heating the material of each of said pixels.
Such a device is used for testing infrared imagery devices, such for example as missile homing devices, by reproducing in the laboratory infrared images as close as possible to those which will be met with in reality.
2. Description of the Prior Art
A device of the above type is already known, described in U.S. Pat. No. 4,572,958 to Durand et al. In this device, the selective heating means comprise an electron beam or laser beam, of small diameter with respect to the dimensions of a pixel, which bombards a portion, in the form of a median strip, of a thin layer of good heat conducting material which extends over an area equal to that of a pixel. The purpose of this layer is both to convert the energy of the beam into heat and to diffuse the heat occurring in the strip shaped portion towards the whole of the surface of the layer and parallel to this layer. Two slabs of heat insulating material, disposed in contact with the preceding layer and on each side of the electron beam path before its impact, slowly diffuse the heat of the layer, perpendicularly this time to this layer and in a direction opposite the displacement of the electrons, towards two layers made from a material having high emissive power in the infrared, in this case two black body layers, whose purpose is to convert the heat into infrared radiation, these two black body layers forming the pixel properly speaking. Naturally, the preceding slabs, as well as the layer for converting the energy of the beam into heat, disposed between the two black body layers and the screen, are transparent to the infrared.
In the case where the beam bringing the energy to the pixels is an electron beam, the device is in the form of a cathode ray tube making it possible to obtain animated infrared images from a video signal of known type.
The structure of the screen of such a device is relatively complex and so of a high cost price. Furthermore the performance of such a device is limited because of the use of a low power beam, this being imposed by its necessarily restricted diameter.